METHYLBENZENE CATION RADICAL ALPHA-FRAGMENTATION SELECTIVITIES REVEALED IN SET-PHOTOADDITIONS OF P-XYLENE DERIVATIVES TO 1,4-DICYANONAPHTHALENE
METHYLBENZENE CATION RADICAL ALPHA-FRAGMENTATION SELECTIVITIES REVEALED IN SET-PHOTOADDITIONS OF P-XYLENE DERIVATIVES TO 1,4-DICYANONAPHTHALENE
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DOI：
10.1021/jo00056a029
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发表时间：
1993-02-12
影响因子：
3.6
通讯作者：
MARIANO, PS
中科院分区：
文献类型：
--
作者：
DALESSANDRO, N;ALBINI, A;MARIANO, PS
研究了对二甲苯（3a）、对苯二乙酸（3b）、对双[（三甲基硅基）甲基]苯（3c）、对[（三甲基硅基）甲基]甲苯（3d）、对甲苯乙酸（3e）和对[（三甲基硅基）甲基]苯乙酸（3f）等对二甲苯衍生物在SET光催化下合成1，4-二氰基萘的反应。这些过程导致清洁和选择性形成的1：1加合物，其性质是由α-杂裂解片段化反应发生在芳烃阳离子自由基，作为关键的反应中间体的苄基位置控制。结果表明，（[ArCH_2 E].+ + B：--> ArCH 2.+ BE）取决于离电基团E的性质，其顺序为：E = SiMe 3> CO 2 H> H。这些结论的实验基础进行了讨论。
SET-promoted photoreactions of selected p-xylene derivatives, including p-xylene (3a), p-phenylenediacetic acid (3b), p-bis[(trimethylsilyl)methyl]benzene (3c), p-[(trim ethylsilyl)methyl]toluene (3d), p-tolylacetic acid (3e), and p-[(trimethylsilyl)methyl]phenylacetic acid (3f), to 1,4-dicyanonaphthalene have been investigated. These processes lead to clean and selective formation of 1:1 adducts whose nature is controlled by alpha-heterolytic fragmentation reactions occurring at benzylic positions of arene cation radicals which serve as key reactive intermediates. The results indicate that the relative rates of cation radical fragmentations of the type ([ArCH2E].+ + B: --> ArCH2.+ BE) depend on the nature of the electrofugal group, E, in the following order: E = SiMe3 > CO2H > H. The experimental basis for these conclusions is discussed.